1. Field of the Invention
This invention relates to an automatic stacker with mechanical or magnetic heads, which is able to stack in an ordered manner in alternate upright and inverted layers rolled metal sections cut to commercial length.
2. Discussion of the Background
Automatic stackers of the aforesaid type are well known to the expert of the art, for example from EP 0099863, EP 0196685 and EP 0318722.
In these stackers the rotary heads, for example magnetic, withdraw an ordered layer of sections from a transport system and position it inverted on a layer of sections previously deposited in an upright position, on a descending platform provided in a forming region for the stack to be packed.
Generally the rotary heads cooperate with to-and-fro moving carriages provided with lances to withdraw from said transport system, alternately with the magnetic heads, those layers of sections to be deposited on the descending platform in an upright position.
In these known stackers, the rotary heads are rotated by complex, costly linkages which, being of rigid geometry, are able to cause the magnetic heads to approach to within only a certain distance from the top of the last layer of sections deposited on the descending platform, from which distance the layer of sections is allowed to drop by demagnetizing the magnetic heads and with the aid of expulsion means.
Dropping of the layer of sections from a certain distance can result in their disordered stacking, and hence a badly made pack, which must be prevented for evident commercial reasons.
In addition, a disordered top layer of sections can interfere with the magnetic head movement, with consequent breakage, jamming and machine stoppage.
Precisely to avoid said interference, the movement path of the magnetic heads is maintained at a certain distance from the top of the lastly deposited layer on the descending piatform, but with said risk of depositing the sections in an imperfectly ordered manner. In addition, the movement of the head carrying a layer of inverted sections towards the layer of upright sections already deposited in the stack formation region takes place along an axis which is not perfectly perpendicular to the plane in which the layer of upright sections lies, this not facilitating the nesting of those sections having more difficultly stackable shapes.
Stackers of a known type also occupy a considerable space above the section transport line, making the operating region difficultly accessible, both from above and laterally (see for example IT 1247451).
Finally, the complexity of the linkages driving the rotary heads means that a multiplicity of manoeuvres are required, leading to a too lengthy stacking time, incompatible with the continuously increasing productivity of modern rolling mills.